Galatians 6:7-8 read, "Do not be deceived, God is not mocked; for whatever a man sows, this he will also reap. For the one who sows to his own flesh shall from the flesh reap corruption, but the one who sows to the Spirit shall from the Spirit reap eternal life."
The Apostle Paul is giving a principle here. He is speaking of the focus of our lives. If you're focusing on the things of the flesh, that's all you're going to get…fleshly gain. To specifically answer your question, you may receive money back or you may not. Paul is not giving instructions for how to have fleshly gain. What he is giving are instructions to receive spiritual rewards instead of fleshly rewards. If you focus your life on spiritual things, you will reap eternal life.
Therefore, if your purpose for giving to any cause is for fleshly gain, the most you can reap from this would be a temporary, fleshly gain, and in the end the loss of opportunity to be a true follower of Christ, who will reap eternal life. However, if your purpose for giving your time, talents, money, or anything you have or are, is to live like Jesus lived, then you will grow spiritually.
As Paul finishes his thought in Galatians 6:9-10, "And let us not lose heart in doing good, for in due time we shall reap if we do not grow weary. So then, while we have opportunity, let us do good to all men, and especially to those who are of the household of the faith."
